Cone protrusion in multi-domain vertically aligned liquid crystal display

ABSTRACT

A pixel unit included in a multi-domain vertically aligned liquid crystal display is provided. The pixel unit includes a first insulating substrate having a first side and a second side, a second insulating substrate having a third side and a fourth side, a plurality of liquid crystal molecules filled between the first side of the first insulating substrate and the fourth side of the second insulating substrate, an electric field generation device for providing an electric field to change alignment of the liquid crystal molecules, and a cone protrusion formed on the first side of the first insulating substrate for generating an advance inclination of the liquid crystal molecules around the cone protrusion.

FIELD OF THE INVENTION

The present invention relates to a pixel unit, and more particularly toa pixel unit included in a multi-domain vertically aligned liquidcrystal display.

BACKGROUND OF THE INVENTION

The current trend is towards liquid crystal displays for achieving alarger panel size and a higher resolution. However, the characteristicsof response time and wide-viewing angles of a liquid crystal display arestill needed to be improved.

In order to improve the response time and the wide-viewing angles, amulti-domain vertically aligned (MVA) liquid crystal display isdeveloped as shown in FIGS. 1(a) and (b). Liquid crystal molecules 13around protrusions 12 which are formed on an upper substrate 10 and alower substrate 11 are aligned with an advance inclination as shown inFIG. 1(a) by the protrusions 12. Therefore, when the liquid crystalmolecules 13 are applied with an electric field, the liquid crystalmolecules 13 are in the inclination state, so that the response time andthe wide-viewing angle are improved.

Please refer to FIGS. 2(a) and (b) showing another type of a multidomainvertically aligned liquid crystal display. The protrusion 22 is onlyformed on the upper substrate 20, and the lower substrate 21 hascorresponding slits 23 thereon. Therefore, the liquid crystal molecules24 are aligned as those in FIG. 1, and the response time and thewide-viewing angle of the multi-domain vertically aligned liquid crystaldisplay are improved.

The fabricating processes of the foresaid multi-domain verticallyaligned liquid crystal display are complex, so that a cruciform bumpstructure 31 formed around a pixel electrode 30 as shown in FIG. 3 isdeveloped. The fabricating process is easier, and the four regionshaving different alignments of the liquid crystal molecules are formed.However, disclination lines are generated at some positions around thepixel electrode, and the transmittance of the panel of the liquidcrystal display are decreased.

The present invention provides a pixel unit for being used in amulti-domain vertically aligned liquid crystal display to overcome theforesaid drawbacks.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a pixel unitincluded in a multi-domain vertically aligned liquid crystal display.

In accordance with present invention, the pixel unit includes a firstinsulating substrate, a second insulating substrate, a plurality ofliquid crystal molecules, an electric field generation device, and acone protrusion.

The first insulating substrate has a first side and a second side.

The second insulating substrate has a third side and a fourth side.

A plurality of liquid crystal molecules are filled between the firstside of the first insulating substrate and the fourth side of the secondinsulating substrate.

The electric field generation device provides an electric field tochange alignment of the liquid crystal molecules.

The cone protrusion is formed on the first side of the first insulatingsubstrate for generating an advance inclination of the liquid crystalmolecules around the cone protrusion.

Preferably, the first substrate and the second substrate are substratespervious to light.

Preferably, the substrates are glass substrates.

In addition, the electric field generation device includes a pixelelectrode formed on the fourth side of the second insulating substrate,and a common electrode formed on the first side of the first insulatingsubstrate.

Preferably, the cone protrusion is disposed above a center of the pixelelectrode.

It is another object of the present invention to provide a method forfabricating a cone protrusion in a fabricating process of a liquidcrystal display.

In accordance with the present invention, the method includes steps ofproviding an insulating substrate, forming a positive photoresist layeron the insulating substrate, performing an exposure on the positivephotoresist layer by using a mask, wherein a masking region of the maskis a pattern having a masking rate decreased progressively from centerto surrounding, and performing a development to remove the positivephotoresist layer and form a cone protrusion on the insulatingsubstrate.

Preferably, the insulating substrate is a substrate pervious to light.

Preferably, the substrate is a glass substrate.

Preferably, the masking region is circle-shaped.

Preferably, the liquid crystal display is a multi-domain verticallyaligned liquid crystal display.

It is another object of the present invention to provide a method forfabricating a cone protrusion in a fabricating process of a liquidcrystal display.

In accordance with the present invention, the method includes steps ofproviding an insulating substrate, forming a negative photoresist layeron the insulating substrate, performing an exposure on the negativephotoresist layer by using a mask, wherein a masking region of the maskis a pattern having a masking rate decreased progressively from centerto surrounding, and performing a development to remove the negativephotoresist layer and form a cone protrusion on the insulatingsubstrate.

Preferably, the insulating substrate is a substrate pervious to light.

Preferably, the substrate is a glass substrate.

Preferably, the masking region is circle-shaped.

Preferably, the liquid crystal display is a multi-domain verticallyaligned liquid crystal display.

The present invention may best be understood through the followingdescriptions with reference to the accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1(a) and (b) are schematic views showing a conventionalmulti-domain vertically aligned liquid crystal display;

FIGS. 2(a) and (b) are schematic views showing another conventionalmulti-domain vertically aligned liquid crystal display;

FIG. 3 is a schematic view showing a cruciform bump structure formedaround a pixel electrode in a conventional multi-domain verticallyaligned liquid crystal display; and

FIGS. 4(a) and (b) are schematic views showing the pixel electrodeaccording to the preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 4(a) and (b) are schematic views showing the structure of themulti-domain vertically aligned liquid crystal display provided by thepresent invention. The multi-domain vertically aligned liquid crystaldisplay includes plural pixel units having the same structures, and onlya pixel unit is shown in FIG. 4. The pixel unit includes a firstinsulating substrate 40 as a color filter, a second insulating substrate41 having switching elements, i.e. a thin film transistor, thereon,plural liquid crystal molecules 45 filled between the first side 401 ofthe first insulating substrate 40 and the second side 412 of the secondinsulating substrate 41.

The pixel unit further includes a pixel electrode 42 formed between thesecond side 412 of the second insulating substrate 42 and the first side401 of the first insulating substrate 40, and a common electrode 43 toform an electric field generation device. The electric field generationdevice provides electric field to change the alignment of the liquidcrystal molecules 45.

A cone protrusion 44 is disposed on the first side 401 of the firstinsulating substrate 40 above the center of each pixel electrode 42. Theliquid crystal molecules around the cone protrusion 44 have an advanceinclination with 360 degree symmetry as shown in FIG. 4(a). When theelectric field generation device provides an electric field, thealignment of the liquid crystal molecules 45 are cone-shaped as shown inFIG. 4(b). Therefore, the viewing angle could be improved and thedisclination lines could be decreased by the cone alignment.

The method for fabricating the foresaid cone protrusion 44 includessteps of forming a positive photoresist layer on the insulatingsubstrate, performing a front or back exposure on the positivephotoresist layer by using a mask, wherein the masking pattern is acircle having a masking rate decreased progressively from the center tosurrounding, and performing a development to remove the exposed positivephotoresist layer. Since the masking pattern is a circle having amasking rate decreased progressively from the center to surrounding, theexposing energy is increased progressively from the center tosurrounding. Therefore, the height of the remaining positive photoresistlayer is decreased progressively from the center to surrounding. Inaddition, if a negative photoresist layer is used in the fabricatingprocess provided by the present invention, the pervious region is acircle having a pervious rate decreased progressively from the center tosurrounding.

The first insulating substrate and the second insulating substrate couldbe glass substrates pervious to light. The cone protrusion could be acone having plural sides and be used in a multi-domain verticallyaligned liquid crystal display.

The present invention provides cone protrusions in each pixel unit of aliquid crystal display. Hence, the viewing angle could be improved andthe disclination lines could be decreased by the alignment of the liquidcrystal molecules with 360 degree symmetry.

While the invention has been described in terms of what are presentlyconsidered to be the most practical and preferred embodiments, it is tobe understood that the invention need not be limited to the disclosedembodiment. On the contrary, it is intended to cover variousmodifications and similar arrangements included within the spirit andscope of the appended claims which are to be accorded with the broadestinterpretation so as to encompass all such modifications and similarstructures. Therefore, the above description and illustration should notbe taken as limiting the scope of the present invention which is definedby the appended claims.

What is claimed is:
 1. A pixel unit comprised in a multi-domainvertically aligned liquid crystal display comprising: a first insulatingsubstrate having a first side and a second side; a second insulatingsubstrate having a third side and a fourth side; a plurality of liquidcrystal molecules filled between said first side of said firstinsulating substrate and said fourth side of said second insulatingsubstrate; an electric field generation device for providing an electricfield to change alignment of said liquid crystal molecules; and a coneprotrusion formed on said first side of said first insulating substratefor generating an advance inclination of said liquid crystal moleculesaround said cone protrusion.
 2. The pixel unit according to claim 1,wherein said first substrate and said second substrate are substratespervious to light.
 3. The pixel unit according to claim 2, wherein saidsubstrates are glass substrates.
 4. The pixel unit according to claim 1,wherein said electric field generation device comprises: a pixelelectrode formed on said fourth side of said second insulatingsubstrate; and a common electrode formed on said first side of saidfirst insulating substrate.
 5. The pixel unit according to claim 4,wherein said cone protrusion is disposed above a center of said pixelelectrode.